This invention relates to forms for concrete and the like and more particularly to an improved unitary article of manufacture for use in assembling such forms in the field.
In constructing walls, foundations, curbs and the like of concrete or similar initially fluid materials which subsequently harden into the desired structure, it is common to fabricate a form consisting of spaced sides or panels defining the exterior side surfaces of the desired structure. It has been proposed in the prior art to provide elongated metal members or form ties adapted to extend between the side panels of a form and temporarily tie the sides or panels of the form to each other while concrete for example is poured into the form and allowed to harden. Such form ties are thus imbedded in the concrete and means are provided for the subsequent release of the form sides from the form ties so that the form sides or panels may be removed for reuse.
U.S. Pat. No. 1,097,796 (Fuehrer) and U.S. Pat. No. 1,729,807 (Toogood) are representative of prior art form ties. However, the form tie disclosed by Fuehrer will not resist either shear forces or transverse forces acting on the form sides unless used in pairs at given locations to form an X-shaped configuration. The form tie disclosed by Toogood will resist transverse forces acting on the form sides when used alone at a given location but will not resist shear forces even if more than one is used at a given location.
U.S. Pat. No. 3,199,827 (Terry) discloses a preassembled, multielement form tie which includes a pair of elements or cross members similar to the form tie described by Toogood interconnected by additional elements being vertical stringer members and diagonal members adapted to resist vertical shear forces. A limitation of such a form tie is the relatively complicated form structure requiring spot welding of the vertical stringer members and the diagonal members to the upper and lower cross members. Furthermore, such a form tie is required to be set in a concrete footing before the panels are attached thereto for forming a stemwall disposed upon the footing. The panels include openings for receiving portions of the form ties therethrough to secure the panels to the form tie. A further limitation of a form tie which is set in the footing is that a precise location of the form tie is required for alignment to the openings in the panels or the openings must be large enough to compensate for any error in the placement of the form ties. Such a compensation will reduce the resistance to horizontal shear forces.
U.S. Pat. No. 4,034,950 (Powell) shows a form tie which is particularly useful when used in a plurality of vertical and horizontal rows in interconnecting the form sides. The positions of all of the form ties may be varied with respect to each other to provide resistance to shear and transverse forces. However, in certain applications, for example, the construction of basement and retaining walls and supporting columns for bridges, roadways and the like, long forms are used, and it is frequently necessary to secure reinforcing steel or rods intermediate the form sides at certain predetermined depths and lateral locations relative to the side panels to attain the desired strength within the concrete structure. A further limitation, therefore, of the prior art form ties is that while reinforcing steel may be supported thereon, the force exerted by the concrete as it is poured into the form may shift the lateral location of the rods, thus weakening the structure.
The foregoing illustrates the limitations of the known prior art. Thus, it is apparent that it would be advantageous to provide an alternative to the prior art.